Football and other sporting events are often played in adverse weather conditions, hence, a headgear is a very desirable accessory at sporting events. Sometimes a headgear is used for warmth. Other times it is used as a sun deflector.
Headgear worn at sporting events is often colorful and humorous. For example there are the well known cheese hats worn at football games in Wisconsin.
Noisemakers are also common at football games. However, when sitting in bleachers, such noisemakers often make it hard to hear announcements.